Even though Jowan is hated in the game, I think that's because he's a bit of a twat, and your character could do the exact same things and not get in a spot of bother. Mind you, not sure what would happen if you're a blood made, and you copulate with Leilana, while in the Tower. That might bring bad some bad memories with Gregor.
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glasntMar 3 '11 at 22:24

if you need an RP perspective, perhaps they overlook it because you are a Grey Warden
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XantecJan 15 '11 at 13:14

As pointed out by @brolin-mislef, it should be noted that doing the quest to become a blood mage will result in Wynn leaving the party - although it is for the actions taken to become a blood mage, not for being a blood mage.
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WipqoznApr 26 '11 at 10:43

@Wipqozn - I finished the game multiple times with Wynne in the party playing as a Blood Mage. There are multiple ways to unlock the specialty, and not all of them result in her departure.
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LessPop_MoreFizz♦Apr 26 '11 at 11:55

Another edit... my third. I kept getting the blood mage quest mixed up with the reaver :/
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WipqoznApr 26 '11 at 12:13

I hear that in the beta, if you were a blood mage, Wynne would refuse to group with you. That probably got changed for obvious reasons, so now you can be a blood mage and use your blood spells in front of anyone, even the Circle of Magi.

It was originally planned for Wynne to call you out on being a Blood Mage while in the presence of Knight Commander Greagoir and First Enchanter Irving at the end of the Broken Circle quest. Dialogue was recorded (as can be seen in a fan made reconstruction), but was cut from the game.

In that cut dialogue, Wynne notes that the spells you are using are not those taught by the Circle and are very powerful and disturbing. You can try to persuade her that it was not Blood Magic, but in fact were special Grey Warden spells (with Greagoir noting that although they may be unsavory, the Grey Wardens had a right to use them if they felt it was necessary and their intentions were good). If you reveal that it is indeed Blood Magic, then Greagoir orders you to be killed. After all, they just went through a whole deal of Blood Mages taking over the Tower and they just found one more.

I imagine that this conversation was cut for two reasons. First, it creates a new outcome in which both the Mages and the Templars turn on you, meaning you don't have either faction as an ally. Second, when you say that they are Grey Warden spells, Wynne notes that "there is only ever one mage Warden at a time" so you had nobody to teach you (Irving reasons that the Grey Wardens had books from past mage Wardens, so you must have learned the spells from them). It seems that the developers decided they didn't want to limit themselves in this way, so they cut the reference to it.

Unfortunately, this means that in the final version of the game your allies, Wynne included, don't seem to care that you're using Blood Magic. However, you can accept this from a roleplaying perspective by imagining that you had an off-screen conversation and managed to convince your companions that they were Grey Warden techniques. If you go so far as to actually make Wynne a Blood Mage, then you can reason that she doesn't fully recognize blood magic (since the only time she has seen it has been briefly during combat) and that she wants to believe the lie that you really are teaching her secret Grey Warden techniques.